This invention relates to subsea assemblies, particularly tree caps for subsea Christmas trees, and a method for placing a tree cap on a subsea assembly with an ROV which is faster and safer than traditional methods.
This invention relates generally to the field of equipment and methods of installation thereof of subsea wellhead equipment. In particular, the invention concerns a ROV deployed cap for a Xmas tree for a subsea well and the method of installing and retrieving the tree cap.
Prior tree caps have been installed by using a drill pipe connector arrangement. Prior tree cap design has been elaborate almost a piece of art. Extensive machining and weight issues became the norm. An extra trip of the drill pipe was required simply to retrieve or lower the tree cap. As the offshore oil industry moves to deeper and deeper depths, the time that it takes to lower or retrieve the tree cap with drill pipe will cost a well operator thousands of dollars in rig time alone.
Accordingly, a primary object of the invention is to provide a lightweight ROV installable tree cap for a subsea Xmas tree.
Another object is to provide a method of installing and retrieving the tree cap by using pressure fluid apparatus for stabbing the cap in place on the production hub and for retrieving the cap.
The present invention is a remotely installed pressure containing closure, such as a tree cap that be easily installed by a ROV (Remotely Operated Vehicle) onto a subsea Xmas tree, and have the capability to test the production seals and annulus seals prior to producing oil via the well.
A remotely installed pressure containing closure, such as a tree cap, for a subsea assembly having at least one fluid bore comprising: a guidance ring having a plurality of chambers; a plurality of pins affixed to said guidance ring for aligning the guidance ring to a finnel; buoyant material disposed in the chambers of said guidance ring; a cylinder connected to a tree cap body for engaging sealing means on a subsea assembly for sealing at least one seal of at least one fluid bore of said subsea assembly; a debris cover connected to said cylinder to house equipment and cover the fluid bore; a mandrel having at least one fluid bore disposed under said debris cover; an actuator secured to said cylinder; a plurality of locking dogs attached to said actuator by a plurality of rotatable rods for locking down said tree cap onto said mandrel; a rotatable handle secured to said actuator; a handle extension rod connected to said handle; a handle locking sleeve connected to said handle extension rod; a locking ring in slidable engagement with said handle locking sleeve for engaging said ring against said subsea mandrel; and at least one dual function stab port for receiving a stab to activate the hydraulic cylinder.
According to a preferred embodiment of the invention, a tree cap can be constructed with a rotatable handle in an actuator, which has slight negative buoyancy, thereby providing a tree cap that can be easily locked into place on a subsea Xmas tree.
The ROV engages a handle secured to an actuator, pressure is applied with a hydraulic means enabling the fluid seals to be secured in place.
The handle is preferably latchable, and the tree cap is self-aligning.
The tree cap is designed to have slight negative buoyancy when submerged so that it may be easily handled by a ROV utilizing buoyant material. Additionally, the tree cap may utilize various components, which have light densities.
The invention also includes the method for installing the novel tree cap.
Other objects, features, and advantages of the invention will be apparent from the following specification and drawings.